1. Field of the Invention
This application concerns the manufacture of a multiple part metal component, such as a connecting rod, by the technique of fracturing an integral single part into multiple portions. The fracture is carried out by applying a tension force across a stress riser groove formed in the single part. The subject application concerns an improved stress riser groove which is formed by laser technology to produce a relatively narrow, deep and sharp V-shaped groove characterized by sharp corners which promotes crack initiation at relatively low tension force levels imposed on the single part.
2. Description of Related Art
The U.S. Pat. No. 3,818,577 to Bailey et al. discloses a connecting rod made essentially by the above identified cracking technique. In Bailey, the location of the crack and resultant fracture is determined by forming a brittle, heat treated frangible zone created by using electron beam bombardment as a localized heat treating process. The patent stipulates that the frangible zone is sufficient to successfully generate the crack. However, a stress concentrating notch circumscribing the frangible zone is also disclosed. The notch, shown in FIGS. 1 and 2, is shallow and wide and presumably is by broaching or other mechanical means, unlike the laser formed stress riser of the present application.
Other references which disclose grooves to initiate and localize a crack during the fracture technique are: U.S. Pat. Nos. 1,630,759; 2,553,935; and 4,693,139. The grooves disclosed in these prior art references are mechanically formed and are wide and shallow compared to the sharp, narrow and deep laser formed groove taught by the subject application.